Self-cleaning electrical precipitator



June 20, 1944.

l. A. YosT ET AL 2,352,061

2 Sheets-Shee t l Filed Nov. 18, 1942 TORS fgward .Pey

' ,ATTORNEY June 20, 1944.

l. A. YOST ET AL 2,352,061 SELF CLEANING ELECTRICAL PRECIPITATCR Filed Nov. 18, 1942 z'sheets-sheet 2 "INVENTORSV- a ma? gczr egg.

ATTORNEY Patented June 20, 1944 saw-mama ELECTRICAL raacirrm'roa Irvine A. Yost and Edward H. R. Pegg, Lakewood,

Ohio, assignors to Westinghouse Electric '& Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 18, 1942, Serial No. 466,020 I 4 Claims. (Cl. 183-7),

Our invention relates to improvements in electrical precipitators for; electrostatically removing foreign particulate matter, hereinafter termed dust or dust-particles, from a flowing gas; which precipitators are of a class having dust-precipitating means comprising a plurality of individually distinct, structurally similar, dust-precipitating sections which are moved successively in a predetermined endless path through a gas-cleaning portion of the precipitator in which the dust-precipitating sections are utilized for gas-cleaning,

and through an electrode or plate-cleaning. portion of the precipitator, in which the dust-precipitating sections are successively subjected to a cleaning action intended. to remove the accumulated collected dust from the sections by the use of a viscous liquid. Each section comprises a plurality of spaced relatively insulated and uninsulated dust-collecting electrodes or plates. The;

sections are arranged compactly along the endless path and are successively passed from the gas-cleaning portion into the plate-cleaning portion and then back to the gas-cleaning portion of the precipitator. described in Patent No. 2,212,885 of August 27, 1940, to-H. W. Pound et al. and in patent-application Serial No. 431,391 of G. W. Penney, filed February 18, 1942, which matured on January 5, 1943, into Patent No. 2,307,603.

An electrical precipitator-unit to which our invention more particularly pertains comprises a dust-precipitating means, as aforesaid, in the form of a curtain having its individually distinct sections movable one after the other in an oblong endless path having its long sides spaced :from' each other longitudinally along the gas-stream,

and extending transversely across the gas-stream.

An endless path of this type is provided with end portions out of the gas-stream, along which each section is moved for reversing its direction of travel. By arranging the endless path vertically, each section of the curtain can be conveniently and automatically cleaned while in an end portion flowing between oppositely chargeddust-collecting plates. The bridging. matter is usually quickly burned up or burst so that such a flashover or spitting is usually momentary. The equivalent of flashovers in the form of arcs may also occur when charging circuits are interrupted or about I I I to be made. Such a flashover, due to circuit-arcs,

may persist until the arcing terminals 'ofthe Circuit are moved to discourage or extinguish the Precipitators of this class are arc. If the circuit is being interrupted, the arcextinction will take place when the terminals are separated a suflicient distance; and if the circuit is being completed, the arc extinction will take Place when the terminals are in conductive engagement or contact. Momentary flashovers'are, as a rule, of too short duration to ignite a combustible oil or oil-soaked collected dust; but flashovers due to circuit-make or -break may, under certain conditions, be of sufliciently long duration to cause the combustible oil to reach inflammable temperatures.

It is accordingly a primary object of our invention to provide an electrical precipitator of a class described, utilizing oil for either cleaning the dust-precipitating sections or coating the plates thereof with a layer of oil for causing dust adherence, in which fire hazards areminimized.

' To this end, our invention is directed to reducing of the endless path by a viscous liquid which is v generally oil, and is so designated hereinafter.

In use, such an electrical precipitator-unit has relatively insulated elements, including the relatively insulated and uninsulated dust-collecting plates of the movable sections, which are oppositely charged by relatively high voltages. Flashovers or spitting occasionally, and sometimes frequently, occur between such oppositely charged elements; being caused generally by a lump of collected relatively conducting dust reducing the gas-insulation between the elements, or by large relatively conducting dust-particles trapped or to a minimum the'quantit'y of cleaning oil iii the Drecipitator and to reducing or eliminating conditions giving rise to excessive circuit-arcs.

A specific mode indicating the application of our inventionin'a preferred form is explained in the following description thereof which is limited to the essential parts necessary for an understanding of our invention. The description is to be taken in connection with the accompanying drawings in which parts have been omitted from some views in the interest of clarity. In these, draw- I ings, in which like numerals refer to like'parts:

Figure 1 is a vertical sectional view of a precipitator-unit' embodying our invention;

' Fig. 21s a detail thereof; a

Fig. 3 is a partial vertical sectional vi w, transverse to Fig.1, of the lower part of the precipitator-unit with the dusteprecipitating curtain re- -moved;

Fla. 4 is a horizontal sectional view. of a lower part of the precipitator-unit; and

F 84 5 is a control system for-operating the plate-cleaning means of our precipitator, 1 i

Referring more particularly to the drawings, the-precipitator=linittoomprlses a vertical housing indicated in its entirety by the reference nu meral 2. Such a housing is adapted to be placed in a gas-conduit or duct means, or be part theretacts being separated a distance equal to the 'sulated'plates across the gas-stream passing of spaced ground electrodes 8 between which are insulatedly supported ionizing wires Ill. The dust-precipitating curtain 6 is disposed within the housing 2, and has the form of a vertical endless oblong with spaced parallel long sides between a gas-inlet l2 immediately in back of,

or on the downstream side of, the ionizing means 4, and a gas-outlet M in back of the curtain. The long sides of the dust-precipitating curtain .extend above and below the upper and lower ends, respectively, of the gas-inlet and gas-outlet and project slightly beyond the other sides thereof. The dust-precipitating curtain comprises a plurality of like dust-precipitating sections l6.

Each dust-precipitating section comprises a like number of spaced alternately relatively insulated and uninsulated plates, the insulated plates being designated by the reference numeral l8 and the uninsulated'plates being designated by the reference numeral 20. The insulated plates of each section are electrically conductively connected together by a jumper means 22; and the uninsulated or grounded plates l8 are electrically connected together by a similar jumper means 24 (Figs. 1 and 4). The jumper means 22 and 24 are spaced transversely along a section and provided with contacts 26 for the insulated plates 28 for the uninsulated plates, by transversely meaning transverse to the direction of gas-flow and tothe direction of movethrough the housing can be oppositely charged for'providing the necessary dust-precipitating field between adjacent plates. Such bar means comprises a narrow bar 46 which the contacts 26 of the sections which are at the front side of the dust-precipitating curtain engage; and a narrow bar 48 of slightly greater length than the bar 46, which the contacts 26 at the back side of the curtain engage. The bars are insulatedly supported by the housing 2 in any suitable manner. Such supporting means may comprise insulators 50 supporting conducting bars 52 which position and conductively connect the contact bars 46 and 48.. An insulated conductor 54, connected to a terminal of a unidirectional source of power, is secured to a bar 52.

The contacts 28 for the uninsulated plates engage an oblong contact bar means 56, more particularly shown in Fig. 2, which follows the path of the contacts, and is conductively connected to the metallic housing2 and thereby grounded. The other terminal of the aforesaid source of power is also grounded.

The sprocket chains 88 are oi! a length which is an integral number oftimes the distance between consecutive contacts 26 or 28; and ,in-

. itially the curtain is arranged so that the conment of the curtain 6. 'The contacts 26 and 28 for each section are transversely aligned.

The dust-precipitating sections I6 are arranged side by side, being mounted on a pair of sprocket chains 30 along the upright end walls of the housing, which mesh with sprocket wheels 32 at the top of the precipitator-unit and sprocket wheels 34 at the bottom of the precipitator-unit. The sprocket chains 88 are preferably constructed of removable small links so that a relatively large number is associated with each section. The sprocket wheels 82 are mounted on a driving shaft 86 having an end protruding beyond an end wall of the housing 2, to. which is secured a driving means for moving the dust-precipitating curtain 6. The lower sprockets 84 are fixed on a vertically adjustable rotatable guide shaft 88.

The driving means for driving the dust-precipitating curtain 6 comprises a' continuously rotating motor 48 (Fig. 5) connected to a speedreducing gearing box 42 which in turn drives the shaft 36 through any suitable mechanical connection. The gearing within the box 42 includes any suitable means for changing the continuous rotation of the motor 48 to intermittent motion for relatively rapidly intermittently moving the dust-precipitating curtain 6 a predetermined distance each time between suitable intervals of a few minutes or so.

Each section I6 is preferably rovided with one contactmovable 26 and one movable contact 28, the corresponding contacts 26 or28 of adjacent sections being substantially aligned in the direction of movement of the curtain]; Q9!!- tacts 26 of the sections l6 next to be placed in the gas-stream or just moved from the gasstream are an adequate distance from the conducting bars 46 and 48 for preventing an arc;- over; and the contacts 26 of the sections l6 in the gas-stream are in full engagement with the bars 46 and 48.

In the operation of the parts thus far described, the motor 48 intermittently drives the shaft 36 in a direction indicated by the broken line arrowcf Fig. 1, moving the curtain 6 intermittently every few minutes a distance equivalent to the spacing'between consecutive contacts 26 or 28, so that the positions and number of contacts 26 associated with the insulated contact bar means 46 and 48 will always be the same. The length of the bars 46 and 48 is so chosen that when the dust-precipitating curtain 6 is moved, an oncoming section l6 will replace the section i6".so that the movable contacts 26 of the section i6 will replace the movable contacts 26" of the section 16" in full engagement with the bar 46. A similar operation takes place with respect to the contacts 26 approachingthe bar 48. The contacts 26 leaving the bars 46 and 48 move from full engagement with the bars to adequate separation therefrom for extinguishing any circuit-breaking arc. Consequently, at no time while the curtain is stationary will any of the contacts 26 be removed only such ashort distance from either bar as would permit a containuing-arc until the movable contact is later moved to an arc-intermpting position leaving a bar, or to full engagement with a bar which it is approaching.

For cleaning the plates of a dust-precipitating I section, a pipe 66 is provided between the sprocket wheels 84 below the shaft 88. The pipe is provided with a plurality of downwardly directed nozzle 68 adapted to discharges-spray of oil across and between the plates oi a section therebelow. A second pipe 84, at the side of the pipe 58, has a plurality of nozzles 66 through is preferably such that the resulting oil-streams will have sufficient force to flush the collected dirt from the dust-collecting plates by an action akinto rapid'erosion. Thus, the dirt layer is completely removed and the plates are entirely cleaned. When a cleaned section moves to a position under the nozzles 86, the plates thereof are subjected to a gas-blast which removes excess oil drops from the plates, leaving onlya thin film thereon. The gas-blast leaving the spaces between the plates is directed toward a bottom for the housing which also functions as a liquid catching basin for the oil discharged through the nozzles 80. Oil drops in the gas-blast hitting this basin sticlcto it and any other oil drops, which may be carried along with the gas-blast are caught in a filter 12 across a gas-exit at the bask side of the housing 2. Preferably, the gas used for the gas-blast is cleaned gas so that the exhausted gas passing through the filter 12 may be discharged directly back into the cleaned gasstream. Baflle means 13 may be provided to limit the tendency of gases from the gas-blast to flow directly to the outlet l4 rather than through tact bar means similar to the'bar means 58 may be substituted for the bars 48 and 48.-

While we have described our invention which we believe at present constitutes the preferred form of embodiment, it is obvious that many modifications may be made therein and equivalent parts substituted.

We claim as our invention:

1.- An electrical belt-type dust-precipitator for cleaning a gas-flow, comprising, in combination, a plurality of dust-precipitator sections, each comprising a plurality of spaced facing rela ively insulated and uninsulated plate-electro es, positioning means for intermittently moving said sections step-by-step through a plurality of successive gas-cleaning positions along a substantially straight side of an oblong endless path, then through an electrode-cleaning portion at a return bend of said path, and then through a An important feature of our invention resides in limiting any accumulation of washing oil in the bottom of the precipitator-unit. To this end the basin I0 is provided with a drain 14 connected to a downwardly sloping pipe 16 which, in turn, is connected to a drain pump 18 which pumps used liquid into a tank or reservoir 80. A supply pump 82 pumps liquid from this reservoir to the supply pipe 58, through an oil filter 84. A baiile 86 in the reservoir 80 deflects liquid pumped by the drain pump 18 towards the bottom of the reservoir.

It is not necessary to have a continuous flow of liquid or gas through the pipe 68 or 54, respectively. For timing these operations the gearing 42 may drive a drum controller 88 in predetermined relation to the movement of the dust-precipitating curtain 6. The drum controller 88 has a contact 90 adapted to engage a brush 82 for causing operation of the supply pump 82 from a time just before the curtain begins to move until a short time after movement has been completed. A contact 94 on the drum controller 88 is adapted to engage a brush 96 for causing 0pplurality of successive gas-cleaning positions along the other substantially straight side of said path, and circuit means for oppositely charging the adjacentplate-electrodes of each section in each of its positions, said positioning means causing said sections to move a predetermined distance which is an aliquot part of the length of said p th, for causing the sections to repeatedly occupy the same positions in consecutive passages of said-path.

2. An electrical belt-type dust-precipitator for cleaning agas-iiow, comprising, in combination, a plurality of dust-precipitator sections, each comprising a plurality of spaced facing relatively insulated and uninsulated plate-electrodes, positioningmeans for intermittently moving said sections step-by-step through a plurality of successive gas -cleaning positions along a substantially straight side of an oblong endless path, then through an electrode-cleaning portion at a return bend of said path, and then through a plurality of successive gas-cleaning positions along the other substantially straight side of said path, and circuit means for oppositely charging the adjacent plate-electrodes ofeach section in each of its positions, comprising an insulated contact bar-means extending along the complete path of movement of said sections, and a plurality of spaced contacts, each fastened to one of said sections, slidably continuously engaging said barmeans.

3. An electrical belt-type dust-precipitator for cleaning a gas-flow, comprising, in combination, a. plurality of dust-precipitator sections, each comprising a plurality of spaced insulated plateerationof the drain pump .18 while the operat- 4 ing pump 82 is operating and for a short time thereafter to insure a complete draining of discharged oil from the basin III. A contact 98 on the drum controller 88 is adapted to engage a the gas-blast being continued for a short time after the supply pump is stopped. The gearing -42 is arranged to drivethe drum controller 88 through one complete cycle in synchronized relation with each intermittent movement of the dust-precipitating curtain 6.

As an alternative modification for eliminating entirely any circuit-making and circuit-breaking of the charging circuit to the plates of the dust.-

- brush [00 for causing the opening of a valve I02 in the gas-supply line to the gas-blast pipe 64;

electrodes, means forintermittently moving said sections step-by-step through a plurality of suc-. cessive gas-cleaning positions along a .substan-' tially straight side of an oblong endless path,

then through an electrode-cleaning portion at a return bend of said path, and then through a plurality of successive gas-cleaning positions along the other substantially straight side of said .same positions in consecutive passa es of said path, and pipe-means, comprising a fixed member in said electrode-cleaning portion inside the 116-" riphery of said path, for removing precipitated dust from each section when. suchsection is in cleaning association with said member.

' e ipitating secti n an in u oblong 7 4. An electrical belt-type'dust-precipitator for circuit means for oppositely charging the adjacent plate-electrodes of each section in each of its positions, a pipe-means in said electrodecleaning portion, inside said oblong path, for discharging a treating liquid into a section associated therewith in said electrode-cleaning portion, and means for causing said pipe-means to periodically discharge said treating liquid in a predetermined time relation to the intermittent m movement of said sections.

. IRVINE A. YOST.

EDWARD H. R. PEGG. 

